The dependence of discharge performance on pre-discharge lithium evaporation in high triangularity H-mode discharges in NSTX

Lithium wall conditioning on graphite plasma facing components has been shown to reduce recycling and edge transport [1], improve energy confinement, and suppress edge localized modes in the NSTX. These benefits increased nearly continuously with the amount of pre-discharge lithium evaporation in medium triangularity discharges [2-5], consistent with cross-field transport increasing with collisionality [6]. Here we show similar results for a comparable dataset with increasing pre-discharge lithium evaporation in high triangularity, high performance discharges in NSTX. We observed a nearly monotonic reduction in recycling, neutral pressure, and increase in H-mode confinement factor with increasing evaporation. The ELM frequency was clearly reduced with increasing lithium, although complete ELM-free operation was not observed in this particular sequence. This suggests that the benefits of lithium conditioning should also apply to the highly shaped plasmas planned in NSTX-U. Comparisons between the high and (previously analyzed) medium triangularity boundary shapes will be presented. \\[4pt] [1] Canik J. M.\textit{, et al.} \textit{Phys. Plasmas} \textbf{18,} 056118 (2011).\\[0pt] [2] Maingi R.\textit{, et al.} \textit{PRL} \textbf{107,} 145004 (2011).\\[0pt] [3] Boyle D. P.\textit{, et al.} \textit{PPCF} \textbf{53,} 105011 (2011). \\[0pt] [4] Maingi, R., \textit{et al. Nucl. Fusion }\textbf{53,} 083001(2012).\\[0pt] [5] Boyle D. P.\textit{, et al.} \textit{J. Nucl. Mater.} \textbf{438,} S979 (2013). \\[0pt] [6] S.M. Kaye, \textit{et al. Nucl. Fusion }\textbf{53,} 063005 (2013).